1. Field of the Invention
The present invention relates to a heat-dissipating unit having a hydrophilic compound film and a method for depositing a hydrophilic compound film, and in particular to a heat-dissipating unit having a hydrophilic compound film with an improved heat-conducting efficiency and a method for depositing such a hydrophilic compound film.
2. Description of Prior Art
Since the operating speed of a modern electronic apparatus becomes higher, more heat is generated by the electronic apparatus and accumulated therein to raise its operating temperature. Thus, people pay more attention to the heat dissipation of electronic elements and chips because the electronic apparatus may break down or overheat if the heat accumulated therein cannot be dissipated to the outside efficiently.
Thus, people try to mount a heat sink, a heat-dissipating module or a fan on the electronic elements and chips for heat dissipation. Further, people also like to use heat pipes because they are very effective in heat conduction. The heat pipe is made of copper or aluminum material. The interior of the heat pipe is provided with a chamber. A wick structure is formed on the inner surface of the chamber. One end of the heat pipe is sealed first and a working fluid is filled in the heat pipe through the other end thereof (i.e., the non-sealed end). Then, a degassing process is performed to make the interior of the heat pipe become a vacuum. Finally, the non-sealed end is sealed to form a vacuum sealed chamber. The heat pipe is often made into a tubular pipe or flat pipe. The wick structure within the heat pipe plays an important role in determining the heat-conducting efficiency of the heat pipe. Especially, the flat heat pipe requires the wick structure to have a large capillary force and a small resistance to liquid flow. However, these two properties seem conflicting in terms of the construction of the heat pipe. In order to solve this conflicting problem, the wick structure is usually treated for improving its surface property. In general, the wick structure is surface-treated to have a better wettability to increase the capillary force of the heat pipe. The most effective way is to form nano-scale microstructures on the surface of the wick structure. For example, the nano-scale microstructures may be made by an etching process, in which a chemical solution is used to etch micro-pits on the surface of the wick structure. However, it is uneasy to control the etching rate of such an etching process. Further, the pollution of the chemical solution is also troublesome.
Taiwan Patent Publication No. I292028 discloses a heat pipe and a method for manufacturing the same. The heat pipe includes a hollow tubular casing having two sealed ends. The inner surface of the hollow tubular casing is formed with a liquid-absorbing core. The surface of the liquid-absorbing core is formed with a hydrophilic coating. A liquid fluid is filled in the liquid-absorbing core and sealed in the hollow tubular casing. The hydrophilic coating includes nano-TiO2, nano-ZnO, nano-Al2O3 or the mixture thereof. The thickness of the hydrophilic coating is in a range of 10 to 200 nanometers, preferably 20 to 50 nanometer.
This patent document discloses a heat-conducting coating formed on the outer surface of the hollow tubular casing. The heat-conducting coating includes a nano-scale film made of carbon, copper, aluminum, or copper-aluminum alloy. The thickness of the heat-conducting coating is in a range of 10 to 500 nanometers, preferably 20 to 300 nanometers.
The liquid-absorbing core includes nano-scale carbon balls or carbon fibers. The thickness of the liquid-absorbing core is in a range of 0.1 to 0.5 millimeters, preferably 0.2 to 0.3 millimeters.
The method for manufacturing the heat pipe includes the steps of: providing a hollow tubular casing, forming a liquid-absorbing core on inner surfaces of the hollow tubular casing, forming a hydrophilic coating on the surface of the liquid-absorbing core; and sealing a working fluid in the hollowing tubular casing and making the interior of the hollow tubular casing vacuum.
The inner and outer surfaces of the hollow tubular casing are surface-treated by a laser texturing process.
The hydrophilic coating is made by a vacuum film deposition method.
However, the above conventional art has to utilize expensive apparatuses and inevitably increases its production cost. Therefore, it has problems of (1) complicated production, (2) high cost, and (3) expensive facilities.